Heart failure remains a major cause of death and economic loss in the USA. Newer therapeutic methods have improved the outlook for many but are ineffective for others. While the recent use of implanted blood pumps has shown encouraging results for support of left heart failure, little progress has been made for complete replacement of both sides of the heart. For patients with severe biventricular failure unresponsive to maximal therapeutic measures, cardiac transplantation or replacement with a total artificial heart (TAH) are the remaining options. Existing TAH devices (Abiocor, Syncardia) are too large for many smaller males and most female patients and are either noisy and require large pneumatic tethered lines, or they are subject to clot formation and strokes, and have proven to be unreliable in clinical practice. The goal of this project is to finalize the development of a new, unique, simplified continuous flow TAH (CFTAH) design, which is comprised of a single pump assembly with two impellers and one motor. This double pump concept includes a single continuously rotating brushless DC motor and pump assembly with a centrifugal pump on both ends of the same shaft, rotating at the same speed. The Specific Aims of the proposed research are: 1) Conduct engineering analysis integrating motor, bearing and pump design to guide refinement of the implantable system for dynamic stability, biocompatibility and hemocompatibility, 2) Develop external electronics to implement and refine our control algorithm, and to demonstrate both its fixed speed and its fail-safe automatic modes of providing adequate and balanced ventricular outputs, while avoiding suction of tissues and atrial pressure imbalance, 3) Perform in vitro system characterization, human blood hemolysis, and endurance testing to verify the CFTAH meets requirements for system performance, resistance to intravascular hemolysis and reliability, and 4) Perform in vivo animal experiments to validate hemodynamic response, biocompatibility, the self regulating mechanical design and automatic speed control mode of operation. This design dramatically reduces the size and complexity of the TAH compared to the devices currently implanted clinically. This design is extremely innovative, exploring radical new concepts in TAH design. The availability of a small, simplified alternative which has a single moving component would address many of the problems seen with existing technologies and provide better management for many patients who presently have no treatment options except transplantation. The overall result would be a TAH that could be implanted into smaller patients with a substantially reduced risk for device failure and morbidity.